An accurate adjustment of the relative position of the rotor, including rotating elements which are arranged thereupon, relative to the stationary elements (casings, etc.) in a gas turbine or steam turbine is vital for an optimum, trouble-free operation and low maintenance intervals. Inaccurate positioning leads to differences in the flow behavior around the circumference, therefore leads to vortices, locally increased temperatures, etc. Furthermore, inaccurate positioning can lead to an eccentric rotor position and to a severe rubbing of the blades on the casing and consequently to damage to the blading.
Positioning and adjustment of the radial position of the rotor has been carried out up to now by displacement of the journal bearing of the rotor. Displacement in the vertical and horizontal directions is achieved by exchanging shims of such a bearing. Positioning accuracy with this method lies within the region of 0.05 mm.
The problem with this procedure is, inter alia, that the journal bearings, integrated into compressor inlet casing and exhaust gas casing, are not easily accessible from the outside. For adjusting the journal bearing, the gas turbine or steam turbine has to be at least partially opened up in a very time-consuming procedure. Based on experience, 6 shifts of 12 hours are required for such an adjustment of the compressor bearing.
After displacement of the journal bearings in the compressor inlet casing, moreover, all the oil scrapers and the coupling alignment have to be adjusted. The time consumption for this is typically about 6 shifts.
The total time consumption for adjustment is correspondingly within the region of about 12 shifts, which amounts to an enormous downtime with corresponding costs.